Soi finfet fins with recessed fins and epitaxy in source drain region

ABSTRACT

Fabrication method for a semiconductor device and structure are provided, which includes: providing an isolation layer at least partially disposed adjacent to at least one sidewall of a fin structure extended above a substrate structure, the fin structure including a channel region; recessing an exposed portion of the fin structure to define a residual stress to be induced into the channel region of the fin structure, wherein upper surfaces of a recessed fin portion and the isolation layer are coplanar with each other; and epitaxially growing a semiconductor material from the recessed exposed portion of the fin structure to form at least one of a source region and a drain region of the semiconductor device.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.15/160,099, filed May 20, 2016 the entire content and disclosure ofwhich is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to semiconductor devices and to methodsfor forming semiconductor devices, and more particularly, to a fin-typefield-effect transistor with recessed fin structure(s).

BACKGROUND

Fin-type field-effect transistor (FinFET) devices continue to bedeveloped to replace traditional planar metal-oxide-semiconductorfield-effect transistors (MOSFETs) in advanced complementary metal oxidesemiconductor (CMOS) technology, due to their improved short-channeleffect immunity and higher on-current to off-current ratio(I_(on)/I_(off)). As is known, the term “fin” refers to a verticalstructure within or upon which are formed, for example, one or moreFinFETs or other fin devices, including capacitors, diodes, etc.

Enhancements in fin device structures and fabrication methods continueto be desired for enhanced performance and commercial advantage.

BRIEF SUMMARY

Certain shortcomings of the prior art are overcome and additionaladvantages are provided through the provision, in one aspect, of amethod for fabricating a semiconductor device which includes, forinstance, providing an isolation layer at least partially disposedadjacent to at least one sidewall of a fin structure extended above asubstrate structure, the fin structure including a channel region;recessing an exposed portion of the fin structure to define a residualstress to be induced into the channel region of the fin structure,wherein upper surfaces of a recessed fin portion and the isolation layerare coplanar with each other; and epitaxially growing a semiconductormaterial from the recessed exposed portion of the fin structure to format least one of a source region and a drain region of the semiconductordevice.

In a further aspect, a semiconductor device which includes, forinstance, a fin structure extended above a substrate structure, the finstructure comprising a channel region of a first height, and a recessedfin portion of a second height that is less than the first height; andan epitaxially-grown semiconductor material extending laterally out fromeach recessed fin portion to form at least one of a source region and adrain region of the semiconductor device, wherein a lower surface of theepitaxially-grown semiconductor material extends, at least in part, in aspaced opposing relation to at least one sidewall of each recessed finportion.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

One or more aspects of the present invention are particularly pointedout and distinctly claimed as examples in the claims at the conclusionof the specification. The foregoing and other objects, features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1A depicts a plan view of one embodiment of a structure obtainedduring semiconductor device fabrication, in accordance with one or moreaspects of the present invention;

FIG. 1B is a cross-sectional view of the structure of FIG. 1A, takenalong line 1B-1B thereof, and illustrating one or more fins extendedabove a substrate structure, in accordance with one or more aspects ofthe present invention;

FIG. 1C is a plan view of the structure of FIG. 1A after providing anisolation layer over the substrate structure and between each finstructure, in accordance with one or more aspects of the presentinvention;

FIG. 1D depicts the structure of FIG. 1C, taken along line 1D-1Dthereof, in accordance with one or more aspects of the presentinvention;

FIG. 1E is a plan view of the structure of FIG. 1C after providing agate structure extending at least partially over the fin(s) and theisolation layer, in accordance with one or more aspects of the presentinvention;

FIG. 1F depicts the structure of FIG. 1E, taken along line 1E-1Ethereof, in accordance with one or more aspects of the presentinvention;

FIG. 1G depicts the structure of FIG. 1E, taken along line 1G-1Gthereof, and illustrates one or more exposed portion(s) of the fin(s),in accordance with one or more aspects of the present invention;

FIG. 1H depicts the structure of FIG. 1G after recessing the exposedportion(s) of the fin(s), in accordance with one or more aspects of thepresent invention;

FIG. 1I depicts the structure of FIG. 1H after epitaxial growth of asemiconductor material from the recessed fin portion(s) to form a sourceregion and a drain region, in accordance with one or more aspects of thepresent invention;

FIG. 1J is a plan view of the structure of FIG. 1I after etching theisolation layer to undercut the semiconductor material disposed over therecessed fin portion(s), in accordance with one or more aspects of thepresent invention;

FIG. 1K depicts the structure of FIG. 1J, taken along line 1K-1Kthereof, and illustrates the semiconductor material disposed over therecessed fin portion(s), in accordance with one or more aspects of thepresent invention;

FIG. 1L depicts the structure of FIG. 1J, taken along line 1L-1Lthereof, and illustrates the isolation layer disposed below the gatestructure, in accordance with one or more aspects of the presentinvention;

FIG. 1M depicts the structure of FIG. 1K after epitaxially growing anadditional semiconductor material over the semiconductor materialdisposed over the recessed fins, in accordance with one or more aspectsof the present invention;

FIG. 1N is a plan view of a resultant structure of FIG. 1M, aftersubsequent fabrication processing which includes, for instance, gatereplacement fabrication process and contact formation over the sourceand drain region, in accordance with one or more aspects of the presentinvention;

FIG. 1O depicts the structure of FIG. 1N, taken along line 1O-1Othereof, and illustrates the replacement gate structure, in accordancewith one or more aspects of the present invention; and

FIG. 1P depicts the structure of FIG. 1N, taken along line 1P-1Pthereof, and illustrates the formation of the contacts over the sourceand drain regions, in accordance with one or more aspects of the presentinvention.

DETAILED DESCRIPTION

Aspects of the present invention and certain features, advantages, anddetails thereof, are explained more fully below with reference to thenon-limiting examples illustrated in the accompanying drawings.Descriptions of well-known materials, fabrication tools, processingtechniques, etc., are omitted so as not to unnecessarily obscure theinvention in details. It should be understood, however, that thedetailed description and the specific examples, while indicatingembodiments of the invention, are given by way of illustration only, andnot by way of limitation. Various substitutions, modifications,additions and/or arrangements within the spirit and/or scope of theunderlying inventive concepts will be apparent to those skilled in theart from this disclosure.

The present invention provides, in part, a method for forming asemiconductor device, for example, FinFET with recessed fin structures,and a source region and a drain region disposed over the recessed finstructure, which advantageously improve circuit performance by exertingasymmetric stress across, for example, the channel region of a FinFETdevice. In operation of a FinFET, when an appropriate voltage is appliedon a gate structure, charge carriers (for instance, electrons (generatedby n-type dopants) or holes (generated by p-type dopants)) flow from asource region to a drain region of the transistor through the channelregion. Several issues may arise during FinFET fabrication processing.These issues could negatively impact performance or yield of integratedcircuits containing the FinFETs. As one skilled in the art willunderstand, the conductivity of the channel region is traditionallyimproved by applying stress to the channel region of the FinFETs. In oneexample, the compressive stress may be applied to the channel region ofa p-type FET (PFET) device and a tensile stress may be applied to thechannel region of an n-type FET (NFET) device which, for instance,increases the mobility of holes or electrons, respectively, therebyincreasing the speed and performance of the FinFETs. By way of example,the residual stress in the channel region may be improved by stressingthe source region and the drain region of the fin structures using, forinstance, epitaxially-grown semiconductor material disposed thereover.Disadvantageously, such epitaxial growth process, for instance, resultsin the semiconductor material being formed on the sidewalls of the finstructures or fins which, for instance, may be ineffective intransferring the stress to the channel regions of the FinFET devices.Alternatively, the fins may be recessed and may be re-grown tofacilitate the epitaxial growth of the semiconductor material. In such acase, as one skilled in the art will understand, the residual stressbeing transferred from the epitaxially-grown semiconductor material maybe dependent upon the depth of the recessed fins. Disadvantageously, asthe size of the technology nodes continues to decrease, the recessing ofthe fins may be prone to loading effects resulting, for instance, inlack of planarity or uniformity of the height of the resultant fins,owing to the fin pitch. This, in turn, could cause performancedegradation of the resultant devices. Further, conventional finrecessing techniques typically involve prolonged recessing to achievethe planarity of the fins which, for instance, risks a complete removalof the fins; thereby destroying the resultant FinFET device.

In one aspect of the present invention, there is disclosed a method forforming a semiconductor device which includes, for instance, providingan isolation layer at least partially disposed adjacent to at least onesidewall of a fin structure extended above a substrate structure, thefin structure including a channel region; recessing an exposed portionof the fin structure to define a residual stress to be induced into thechannel region of the fin structure, wherein upper surfaces of arecessed fin portion and the isolation layer are coplanar with eachother; and epitaxially growing a semiconductor material from therecessed fin portion to form at least one of a source region and a drainregion of the semiconductor device.

In one embodiment, the epitaxially growing of the semiconductor materialmay include epitaxially growing the semiconductor material to extendlaterally out from the recessed fin portion to define a lower surface ofthe at least one of the source region and the drain region, with thelower surface extending, at least in part, in a spaced opposing relationto the at least one sidewall of the fin structure. In oneimplementation, the lower surface of the at least one of the sourceregion and the drain region extends symmetrically laterally out from therecessed fin portion. Further, in another implementation, thesemiconductor material may include, or be fabricated of, a stressormaterial (for example, a silicon germanium material), where theepitaxial growth of the semiconductor material over the recessed finportion exerts an asymmetric stress across the channel region of the finstructure. For instance, the residual stress to be induced into thechannel region of the fin structure may be dependent on the height ofthe recessed fin portion, with the total height of the recessed finportion may be within a range from about 2 nm to about 5 nm.

Further, and in another embodiment, the fin structure may includeopposite first and second sidewalls, with the isolation layer beingdisposed adjacent to the first sidewall and the second sidewall onopposite sides of the fin structure. In this example, the recessing ofthe exposed portion of the fin structure may include mechanicallystabilizing the exposed portion of the fin structure with the isolationlayer during the recessing thereof. The fabrication method may furtherinclude a gate structure extending at least partially over the finstructure and over the isolation layer, where the recessing of theexposed portion of the fin structure may include recessing the exposedportion of the fin structure, along with the isolation layer, with therecessing being terminated, at least in part, at a lower surface of thegate structure. In yet another embodiment, the fabrication method mayfurther include etching the isolation layer, subsequent to the epitaxialgrowth of the semiconductor material, to undercut the semiconductormaterial disposed over the recessed fin portion, while leaving, at leastin part, the isolation layer disposed below the gate structure.

In another embodiment, the epitaxially growing may further includeepitaxially growing an additional semiconductor material over thesemiconductor material to increase a width of the at least one of thesource region and the drain region. Further, the additionalsemiconductor material encapsulates the semiconductor material, alongwith the recessed fin portion, with the additional semiconductormaterial enhancing an asymmetric stress generated across the channelregion of the fin structure. The semiconductor material may include, orbe fabricated of, a first silicon germanium material having a firstgermanium content, and the additional semiconductor material mayinclude, or be fabricated of a second silicon germanium material havinga second germanium content, with the first germanium content beingdifferent from the second germanium content.

In yet another aspect of the present invention, there is provided asemiconductor device which includes: a fin structure extended above asubstrate structure, the fin structure including a channel region of afirst height, and a recessed fin portion of a second height that is lessthan the first height; and an epitaxially-grown semiconductor materialextends laterally out from each recessed fin portion to form at leastone of a source region and a drain region of the semiconductor device,wherein a lower surface of the epitaxially-grown semiconductor materialextends, at least in part, in spaced opposing relation to at least onesidewall of each recessed fin portion.

Reference is made below to the drawings, which are not drawn to scalefor ease of understanding, wherein the same reference numbers usedthroughout different figures designate the same or similar components.

By way of example, FIGS. 1A-1P depict one embodiment of a method forforming a semiconductor device, for example, a FinFET with recessed finstructures, and a source region and a drain region disposed over therecessed fin structure, in accordance with one or more aspects of thepresent invention. Advantageously, as described below, the height ofrecessed fins define the residual stress being induced into the channelregion of the FinFET device and the source region and drain regionextends laterally out from the recessed fins.

FIGS. 1A and 1B are various views of one embodiment of a structure 100obtained during a semiconductor device fabrication, in accordance withone or more aspects of the present invention. In the example shown,structure 100 includes a substrate structure 102, which may be (in oneexample) a bulk semiconductor material such as, for example, a bulksilicon wafer. As another example, substrate structure 102 may be anysilicon-containing substrate including, but not limited to, silicon(Si), single crystal silicon (Si), polycrystalline Si, amorphous Si orthe like. Substrate structure 102 may in addition, or instead, includevarious isolations, dopings and/or device features. Optionally, althoughnot depicted in figures, substrate structure 102 may include insulatingsubstrate layer which, for instance, may be, or include, a burieddielectric layer such as, for example, a buried oxide (BOX) layer,silicon-on-nothing (SON), silicon-on-insulator or the like. As oneskilled in the art will understand, a buried oxide layer may befabricated by employing SIMOX (Separation by Implanted Oxygen) techniquewhich, for instance, may include implanting high doses of oxygen (O⁺)ions into the silicon substrate, and annealing at a high temperature toform a layer of buried oxide over the silicon substrate. In such anexample, the fabrication of the buried oxide layer may result in aresidual layer of semiconductor material (not shown) which, forinstance, may include a silicon material, being disposed over theinsulating substrate layer (not shown).

Continuing with FIGS. 1A and 1B, one or more fin structures or fins 104may be formed extending from substrate structure 102. By way of anexample, fins 104 may be formed by patterning one or more portions ofsubstrate structure 102, thereby creating one or more fins 104 of thesame material as the substrate structure 102, for example, siliconmaterial. In one example, formation of fins 104 may be achieved bypatterning the substrate structure 102 using any of various approachesincluding: direct lithography; sidewall image transfer technique;extreme ultraviolet technique (EUV); e-beam technique; litho-etchlitho-etch or litho-etch litho-freeze. Following patterning, the removalmay be performed, for example, by any suitable etching process, such as,anisotropic dry etching processes, for instance, reactive-ion-etching(RIE) process. Although the following numbers are relative and theheights may vary, as one example, fins 104 may have a height of about 20nm to about 100 nm, and a fin pitch of about 30 nm to about 80 nm. Asused herein, “fin pitch” refers to the distance between adjacent finsmeasured from, for example, a middle point of one fin to a middle pointof the adjacent fin. In one example, adjacent fins 104 are separated bya respective opening 106.

FIGS. 1C and 1D are various views of the structure of FIGS. 1A-1B afterforming an isolation layer 108 between each fin 104 and each opening106. By way of an example, the isolation layer 108 may be, or include,an oxide material, such as, silicon oxide, or a flowable oxide material,and may be deposited using a variety of techniques such as, for example,chemical vapor deposition (CVD), plasma-enhanced CVD, sub-atmosphericpressure thermal CVD (SACVD) processes, spin-on coating and the like. Anetch-back process may be employed subsequent to the deposition of thematerial that provides the isolation layer 108. The isolation layer 108,depending on the desired circuit design, may have a thickness from about50 nm to about 200 nm. The isolation layer 108 may, additionally, serveto electrically isolate the resultant FinFET devices. As depicted inFIG. 1D, and in one example, isolation layer 108 has been provided atleast partially within the openings 106 (see FIG. 1B) separating thefins 104, thereby exposing one or more sidewalls 110 of fins 104.

FIGS. 1E-1G are various views of the structure of FIGS. 1C-1D afterproviding a gate structure 112 extending at least partially over thefin(s) 104 and the isolation layer 108, in accordance with one or moreaspects of the present invention. As depicted, the gate structure 112may extend over fins 104, and may overlap fins 104 in selected areas tooperate as, for instance, the gate of a fin-type transistor. As oneskilled in the art will understand, a gate material (not shown) may beprovided over one or more layers (not shown), such as, for instance, agate dielectric layer and/or work function layer to form gate structure112. In one example, the gate material may include, or be fabricated of,a metal, and may be formed as a part of a gate-first fabricationprocess. In this example, the gate dielectric layer may include, or befabricated of, a high-k dielectric material with a dielectric constant kgreater than the dielectric constant of silicon dioxide (k=3.9 forSiO₂), and may be deposited by performing a suitable deposition process,such as atomic layer deposition (ALD), chemical vapor deposition (CVD)or the like. In a particular example, dielectric layer 114 may have adielectric constant greater than 4.0, and more preferably, greater than8.0. Examples of high-k dielectric materials which may be used in thedielectric layer include, but are not limited to, HfO₂, ZrO₂, La₂O₃,Al₂O₃, TiO₂, SrTiO₃, LaAlO₃, Y₂O₃, HfO_(x)N_(y), ZrO_(x)N_(y),La₂O_(x)N_(y), Al₂O_(x)N_(y), TiO_(x)N_(y), SrTiO_(x)N_(y),LaAlO_(x)N_(y), Y₂O_(x)N_(y), and a silicate thereof, and an alloythereof, where x=0.5 to 3, and y=0 to 2. The gate material (not shown)disposed over the gate dielectric layer may include, or be fabricated ofa material such as, for instance, zirconium, tungsten, tantalum,hafnium, titanium, aluminum, or the like.

Alternatively, in another example, the gate material may include, or befabricated of, a sacrificial gate material, such as an amorphous silicon(a-Si) or polycrystalline silicon (polysilicon), which may subsequentlybe replaced with a replacement gate material, as part of a gate-lastfabrication process. Further, although not depicted in the figures,sidewall spacers which, for instance, may include or be fabricated of, anitride material (such as, for example, SiN or Si₃N₄), may be providedalong the sidewalls of the gate structure 112. As understood, thesesidewall spacers, for example, having a thickness from about 4 nm toabout 12 nm, may be conformally deposited using a variety of techniques,such as, for instance, chemical vapor deposition (CVD) or atomic layerdeposition (ALD) processes.

As shown in FIG. 1F, the gate structure 112 wraps up, over and aroundthe fins 104. Further, as depicted, the gate structure 112 also extends,for instance, at least partially over the isolation layer 108 separatingthe fins 104. In this example, the portion of the fins 104 underlyingthe gate structure 112 acts as a channel region 114 of the resultantFinFET device.

FIG. 1G illustrates one or more exposed portion(s) of the fin(s), inaccordance with one or more aspects of the present invention. Asdepicted and discussed further below, the source region and the drainregion are to be provided over the exposed portion of the fins, notcovered by the gate structure 112, during the subsequent fabricationprocessing.

FIG. 1H illustrates the structure of FIG. 1G after recessing the exposedportion(s) of the fin(s) 104 (see FIG. 1G) to form recessed fins 104′,in accordance with one or more aspects of the present invention. In thedepicted embodiment, the recessing of the exposed portions of the fins104 to a desired height, advantageously, facilitates defining a residualstress being induced into the channel region 114 (see FIG. 1F)underlying the gate structure 112 (see FIG. 1F). Although the numbersare relative and the desired height of the recessed fins 104′ may varyaccording to the technology node in which the semiconductor device isbeing fabricated, in one example, the exposed portions of the fins maybe recessed down to a height within a range from about 2 nm to about 5nm. By way of example, such recessing of the exposed portions of thefins 104 (see FIG. 1G) may be accomplished using one or more isotropicetching processes such as, reactive ion etching (RIE) and the exposedportion of fins 104 (see FIG. 1G) may be etched down to an upper surfaceof the isolation layer 108 (see FIG. 1G). Note that, the isolation layer108 separating the fins 104 (see FIG. 1G) facilitates providingstructural stability to the fins during the recessing process, therebymechanically stabilizing the exposed portions of fins. The result isthat the upper, exposed surfaces of the recessed fins 104′ aresubstantially coplanar with each other, as well as with an upper surfaceof the isolation layer 108. Although not depicted in the figures, in oneembodiment, the recessing of the exposed portion of the fins proceeds toat least partially recess the isolation layer 108 along with the exposedfin portions, terminating, in this example, at a lower surface of thegate structure 112 (see FIG. 1E), thereby self-limiting the etchingdistance at the lower surface thereof. This prolonged recessing resultsin further reducing the fin height; thereby inducing additional stressinto the channel region 114 (see FIG. 1F) underlying the gate structure112. Note that there is no variation in height between the uppersurfaces of the recessed fins 104′ and recessed isolation layer 108′,due to such prolonged recessing, since the previously recessed uppersurface of the recessed fins 104′ is substantially coplanar with theupper surface of the isolation layer.

FIG. 1I depicts the structure of FIG. 1H after epitaxially growing asemiconductor material from the exposed upper surfaces of the recessedfins 104′ to form, for example, a source region and drain region(collectively S/D region 118) of a fin-type transistor, such as, theresultant FinFET device. By way of example, the S/D region 118 may beformed by epitaxially growing the semiconductor material from theexposed upper surface of the recessed fins 104′, using selectiveepitaxial growth processes such as, for example, CVD, low-pressure CVD(LPCVD) or other applicable methods. As used herein, “epitaxiallygrowing/growth” refers to the orderly growth of a semiconductor materialover a surface of another semiconductor material, such as, recessed fin104′, where the grown material arranges itself in the same crystalorientation as the underlying material. In one example, thesemiconductor material may include, or be fabricated of any conventionaldoped or undoped semiconductor material such as, silicon, germanium,silicon-germanium alloy, carbon-doped silicon, carbon-doped silicongermanium, and compound (e.g., III-V and II-VI) semiconductor materialsor the like.

As depicted, the epitaxially growing of the semiconductor material fromthe upper surface of the recessed fins 104′ proceeds by extendinglaterally out from the recessed fins 104′, with the semiconductormaterial growing symmetrically and, at least partially, residing overthe upper surface 116 of the recessed isolation layer 108′. In theembodiment illustrated, the lower surface of the S/D region 118 is, inpart, in spaced opposing relation to the sidewall of recessed fins 104′.Further, as one skilled in the art will understand, owing to differencein growth rates of different crystallographic orientations, theepitaxial growth of the semiconductor material may define the shape ofthe S/D region 118 resulting, for instance, in shaped-structures suchas, diamond shaped structures.

Additionally, the epitaxially grown semiconductor material of the S/Dregion 118 which, for instance, may include a stressor material, mayexert asymmetric stress across the channel region 114 (see FIG. 1F)underlying the gate structure 112 (see FIG. 1F). In one embodiment, theamount of the asymmetric stress exerted across the channel region 114(see FIG. 1F) by the epitaxially grown semiconductor material isdependent on the height of the recessed fin 104′. For instance, theshorter the height of the recessed fin 104′, the more efficient is thetransfer of the stress from the epitaxially-grown semiconductor materialof the S/D region 118.

Continuing with FIG. 1I, the stress applied by the epitaxially-grownsemiconductor material of the S/D region 118 to the channel region 114(see FIG. 1F) underlying the gate structure (see FIG. 1F) may betailored to be a compressive stress or a tensile stress, depending uponthe type of the transistor being fabricated. For example, transistorssuch as, PFETs may have holes as majority charge carriers, andcompressive stress may increase the mobility of such charge carriers. Insuch an example, silicon germanium (SiGe), with about 25% to 80% atomicconcentration of germanium may be used to achieve the compressivestress. Additionally, the silicon germanium material may be doped withp-type dopants, such as, boron having a dopant concentration of about2×10²⁰ atom/cm³ to about 2×10²¹ atom/cm³, to enhance the compressivestress within the channel region 114 (see FIG. 1F). In another example,transistors, such as, NFETs may have electrons as charge carriers, andtensile stress may increase the electron mobility. In such an example,carbon-doped silicon material, having about 0.5% to about 2.5% atomicconcentration of carbon, may be used to achieve the tensile stress.Additionally, the carbon-doped silicon material may be doped with n-typedopants such as, arsenic having a dopant concentration of about 2×10²⁰atom/cm³ to about 2×10²¹ atom/cm³ to enhance the tensile stress withinthe channel region (see FIG. 1F).

FIGS. 1J-1L are various views of the structure of FIG. 1I after etchingthe recessed isolation layer 108′ (see FIG. 1I), in accordance with oneor more aspects of the present invention. The recessed isolation layer108′ may be etched using a directional etching process, such as,reactive ion etching (RIE) or plasma etching, to partially undercut theepitaxially-grown semiconductor material 118 disposed over the recessedfins 104′, as illustrated in FIG. 1K. Note that, as depicted in FIG. 1L,the presence of the gate structure 108 may serve to limit theanisotropic etching, because, for example, the thickness of the gatestructure could laterally limit the etching of the recessed isolationlayer 108′ below the gate structure 112 by blocking a portion of theanisotropic etching from reaching below the gate structure, independentof the etch time or other process parameters employed. In one example,the recessed isolation layer 108′ may be etched via an aqueoushydrofluoric acid (HF) etching process.

FIG. 1M depicts the structure of FIG. 1K after epitaxially growing anadditional semiconductor material 120 over the semiconductor material ofthe S/D region 118, in accordance with one or more aspects of thepresent invention. As illustrated, the additional semiconductor material120, in one embodiment, fills the undercut region of the semiconductormaterial disposed over the recessed fins 104′, thereby encapsulating thesemiconductor material and the recessed fins 104′. This, for instance,facilitates increasing the width of the S/D region 118, which, in turn,enhances the asymmetric stress exerted across the channel region 114(see FIG. 1F) underlying the gate structure 112 (see FIG. 1F). By way ofan example, the additional semiconductor material may include, or befabricated of, any conventional doped or undoped semiconductor materialsimilar to the epitaxially grown semiconductor material using any of themethods described above in connection with FIG. 1I. For instance, theadditional semiconductor material may be, or include, semiconductormaterial such as, for example, silicon, germanium, silicon-germaniumalloy, carbon-doped silicon, carbon-doped silicon germanium, andcompound (e.g., III-V and II-VI) semiconductor materials or the like.Further, in one embodiment, the semiconductor material and theadditional semiconductor material may include similar semiconductormaterial, having varying atomic and/or dopant concentrations. In anotherexample, the semiconductor material may include an undoped semiconductormaterial, while the additional semiconductor material disposed thereovermay include a doped semiconductor material having the same material asthe undoped semiconductor material.

FIGS. 1N-1P are various views of a resultant structure of FIG. 1M, aftersubsequent fabrication processing including, for instance, gatereplacement fabrication process and contact formation over the S/Dregion 118 and additional semiconductor material 120 (see FIG. 1M), inaccordance with one or more aspects of the present invention. In thedepicted embodiment, assuming that the gate structure is a sacrificialgate structure, the gate material of the gate structure may besubsequently replaced with a replacement gate material 112′, as part ofa gate-replacement fabrication process. Note that, as shown in FIG. 1N,the recessed isolation layer 104′ may be etched, prior to forming thereplacement gate material 112′.

FIG. 1O illustrates the formation of the contacts 122 over the S/Dregion 118 and additional semiconductor material 120, in accordance withone or more aspects of the present invention. Although not depicted inthe figures, a silicide may optionally be formed using a metal such as,cobalt, nickel, titanium, tantalum, platinum, palladium, rhodium andcombinations thereof, that has been chemically reacted with thesemiconductor material (such as, for example, silicon) of S/D region 118and additional semiconductor material 120. Further, the contact 122(i.e. S/D contact) may be formed by, for instance, by providing aconductive material over the respective silicide (not shown). Theconductive material may be formed by employing one or more conventionaldeposition processes such as, for example, sputtering, plating,evaporation, chemical vapor deposition (CVD), plasma enhanced chemicalvapor deposition (PECVD), chemical solution deposition, atomic layerdeposition (ALD) or the like. In one example, the conductive materialmay be or include a metal such as, for example, tantalum (Ta), tantalumnitride (TaN), titanium (Ti), titanium nitride (TiN), tungsten (W),tungsten nitride (WN) or combinations thereof.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise” (andany form of comprise, such as “comprises” and “comprising”), “have” (andany form of have, such as “has” and “having”), “include” (and any formof include, such as “includes” and “including’), and “contain” (and anyform of contain, such as “contains” and “containing”) are open-endedlinking verbs. As a result, a method or device that “comprises”, “has”,“includes” or “contains” one or more steps or elements possesses thoseone or more steps or elements, but is not limited to possessing onlythose one or more steps or elements. Likewise, a step of method or anelement of a device that “comprises”, “has”, “includes” or “contains”one or more features possesses those one or more features, but is notlimited to possessing only those one or more features. Furthermore, adevice or structure that is configured in a certain way is configured inat least that way, but may also be configured in ways that are notlisted.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of the present invention has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the invention in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The embodiment was chosen and described in order to best explain theprinciples of one or more aspects of the invention and the practicalapplication, and to enable others of ordinary skill in the art tounderstand one or more aspects of the present invention for variousembodiments with various modifications as are suited to the particularuse contemplated.

What is claimed is:
 1. A semiconductor device comprising: a finstructure extended above a substrate structure, the fin structurecomprising a channel region of a first height, and a recessed finportion of a second height that is less than the first height; and anepitaxially-grown semiconductor material extending laterally out fromthe recessed fin portion to form at least one of a source region and adrain region of the semiconductor device, wherein a lower surface of theepitaxially-grown semiconductor material extends, at least in part, inspaced opposing relation to at least one sidewall of the recessed finportion.
 2. The semiconductor device of claim 1, wherein the recessedfin portion induces a residual stress into the channel region of the finstructure, the residual stress being dependent on a height of therecessed fin portion.
 3. The semiconductor device of claim 1, whereinthe lower surface of the epitaxially-grown semiconductor materialextends symmetrically out from the recessed fin portion.
 4. Thesemiconductor device of claim 1, wherein the epitaxially-grownsemiconductor material comprises a stressor material, theepitaxially-grown semiconductor material over the recessed fin portionexerts an asymmetric stress across the channel region of the finstructure.
 5. The semiconductor device of claim 1, further comprising anadditional semiconductor material disposed over the epitaxially-grownsemiconductor material, the additional semiconductor material increasinga width of the at least one of the source region and the drain region.6. The semiconductor device of claim 5, wherein the additionalsemiconductor material encapsulates the epitaxially-grown semiconductormaterial, along with the recessed fin portion, the additionalsemiconductor material enhancing an asymmetric stress generated acrossthe channel region of the fin structure.
 7. The semiconductor device ofclaim 5, wherein the epitaxially-grown semiconductor material comprisesa first silicon germanium material having a first germanium content, andthe additional semiconductor material comprises a second silicongermanium material having a second germanium content, the firstgermanium content being different from the second germanium content. 8.The semiconductor device of claim 1, further comprising an isolationlayer disposed at least partially adjacent to at least one sidewall ofthe recessed fin portion wherein the epitaxially-grown semiconductormaterial extending laterally out from the recessed fin portion residesover an upper surface of the isolation layer.
 9. The semiconductordevice of claim 8, further comprising a gate structure extending atleast partially over the fin structure, wherein the isolation layer isdisposed below a lower surface of the gate structure, while being absentadjacent to the at least one sidewall of the recessed fin portion.